Lead assembly and methods including a push tube

ABSTRACT

A lead assembly includes an elongate body having a conductor electrically coupled with an electrode coupled to the elongate body. The lead assembly includes a push tube extending along at least a portion of the elongate body. A distal tip is coupled to the elongate body substantially adjacent to the distal end of the elongate body. The distal tip is sized and shaped to couple with a push tube distal end. In one option, the distal tip includes a seat to receive the push tube distal end. In another option, the seat is a side rail seat and a guide wire extends along the elongate body and is slidably coupled with the side rail seat. The lead assembly includes, optionally, an active fixation device slidably coupled with a portion of the elongate body, and the active fixation device is sized and shaped to couple with the push tube.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.10/919,202, filed on Aug. 16, 2004, entitled “Lead Assembly and MethodsIncluding a Push Tube,” which is incorporated herein by reference in itsentirety for all purposes. Additionally, this application is related toco-pending and co-owned U.S. application Ser. No. 12/163,869, entitled“Lead Assembly and Methods Including a Push Tube,” which is alsoincorporated herein by reference in its entirety for all purposes.

TECHNICAL FIELD

A lead assembly including a push tube and in particular to a leadassembly having a push tube for positioning leads and fixation devicesin or around a heart.

BACKGROUND

It is often difficult to navigate flexible cardiac leads throughtortuous vasculature for implantation within the vasculature or theheart. The deformable nature of some leads makes it difficult to pushthe lead through the twisting vasculature with a stylet. The leads bendunpredictably and lodge within the veins and arteries. Additionally,leads often include fixation features that snag on the vasculature orprovide a larger profile during navigation. Leads with fixation featuressometimes require multiple stylets to try navigation of the lead aroundcorners or the like. The procedures are further complicated by enlargingthe outer perimeter of leads to accommodate stylet lumens. Such lumensare often defined by coiled conductors that extend through the lead tocouple with electrodes. The coiled conductors and the lumens take upspace within the lead and enlarge the lead profile. Navigation of largerleads is complicated especially in tortuous vasculature, such as aroundthe left side of the heart.

One example of an arrangement for implanting a lead is shown in U.S.Pat. No. 5,902,331. The apparatus described includes a lead havingfixation features at the distal end. The lead is coupled to a guide bodyand moved along the guide body with a pusher wire. The fixation featuresof the lead are one disadvantage of this arrangement. Navigating thelead through vasculature, such as around the left side of the heart isdifficult because the fixation features can undesirably lodge invasculature tissue prior to reaching the desired implantation location.Additionally, the pusher wire is constrained from lateral movement atthe distal end of the lead. If the lead becomes lodged within thevasculature the pusher wire can bow proximally to the distal end andaggravate the tissues of the vasculature. With the use of an introducingcatheter around the entire arrangement the pusher wire is constrainedfrom bowing to some extent, however the introducer catheter undesirablyincreases the outer perimeter of the apparatus and complicatesnavigation of the lead through vasculature.

Another example of an arrangement for implanting a lead is shown in U.S.Pat. No. 6,129,749. The apparatus includes a molded support body for aguide wire. The lead includes a lumen within the elongated lead bodysized and shaped to receive a stylet. The stylet is used to move thelead over the guide wire into a desired orientation. One disadvantage ofthis arrangement is the elongated lead body is enlarged to accommodatethe stylet. The lumen for the stylet is defined by a helically woundcoil. The lumen and the wound coil increase the outer perimeter of thelead and navigation of the larger lead is complicated within tortuousvasculature.

U.S. Pat. No. 6,129,750 shows another example of an arrangement forimplanting a lead. The apparatus includes a coil that has a naturallynon-linear shape. The coil is deployed through a lumen of anover-the-wire lead and constrained from assuming the non-linear shape.When positioned where desired, the coil is released to assume thenon-linear shape and engage the lead against the vessel wall. Adisadvantage of this arrangement is that a coil has a relatively thickprofile that is difficult to navigate through tortuous vasculature.Additionally, the coil is not securely engaged to the lead to permitrotation of the coil along with the lead to enhance contact with adesired surface within the vasculature (e.g., the myocardium of aheart).

What is needed is an assembly for positioning leads that overcomes theshortcomings of previous designs. What is further needed is an assemblycapable of positioning leads and fixation devices within torturousvasculature.

SUMMARY

A lead assembly for positioning leads or placing fixation devicesincludes an elongate body extending from a proximal end to a distal end.In one option, at least one conductor is disposed within the elongatebody and in electrical communication with at least one electrode. Inanother option, the electrode is coupled to the elongate body. A pushtube (e.g., a tube, integral tubing to the elongate body, catheter, orthe like) extends along at least a portion of the elongate body. Atleast a portion of the push tube is more flexible than another portionof the push tube, in one option. The push tube distal end, in oneexample, is more flexible than another portion of the of push tube.Optionally, at least a portion of the push tube includes a grooveextending at least part way between an outer perimeter of the push tubeand an inner perimeter of the push tube. A distal tip is optionallycoupled to the elongate body substantially adjacent to the distal end.The distal tip, in one option, is sized and shaped to couple with a pushtube distal end. In another option, the outer perimeter of the distaltip tapers from a proximal portion of the distal tip toward a distalportion of the distal tip. In yet another option, an outer perimeter ofthe distal tip includes a seat sized and shaped to receive a distal endof the push tube. In still another option, the elongate body issubstantially adjacent (e.g. juxtaposed) to the push tube and the seat.

Optionally, at least one of the push tube distal end and the seat has anoncircular outer perimeter and the other of the push tube distal endand the seat has a corresponding inner perimeter. The seat, in yetanother option, includes a socket sized and shaped to grasp andimmobilize the push tube distal end. In one example, the seat includes adeformable coil disposed within the socket, and the deformable coil hasan inner perimeter smaller than the outer perimeter of the push tube.

A method for positioning leads or placing fixation devices includesguiding a lead assembly over a guide wire, wherein the guide wire isslidably coupled to a side rail seat substantially adjacent to a distalend of the lead assembly. In one option, the side rail seat is disposedalong the lead assembly. A push tube coupled to the side rail seat ismoved over the guide wire, and the side rail seat and lead assembly movewith the push tube. The push tube distal end is more flexible thananother portion of the push tube, in another option. The method includesdeflecting the push tube distal end (e.g. to facilitate navigation intortuous vasculature), optionally.

Several options for the method follow. In one option, the methodincludes coupling the push tube with the side rail seat. Optionally, apush tube distal end is seated within a socket in the side rail seat. Asurface defining the socket is sized and shaped, optionally, toimmobilize at least the push tube distal end. In another option,coupling the push tube with the side rail seat includes coupling thepush tube distal end having a key with the side rail seat having acorresponding recess. The method includes rotating the side rail seatand the lead assembly with the push tube, in yet another option.

In another option, an active fixation device is moved over the guidewire and/or the elongate body toward the lead assembly distal end withthe push tube. The active fixation device is coupled with a distal tipcoupled to the elongate body substantially adjacent to the distal end,in one option. Optionally, a combined outer perimeter of the activefixation device and the distal tip is greater than an outer perimeter ofthe distal tip. The active fixation device is immobilized, for instance,in surrounding tissue, by wedging the active fixation device and thedistal tip within a vein or artery, in one option. In another option,the active fixation device is immobilized by expanding in surroundingtissue to engage the tissue. Immobilizing the active fixation device insurrounding tissue includes engaging a textured surface againstsurrounding tissue, in yet another option.

The above described assembly allows for implantation of slender leadsthrough tortuous vasculature (e.g. coronary veins around the left sideof the heart) using a push tube. In one option, the lead assemblyincludes a distal tip sized and shaped to couple with a push tube thatextends along at least a portion of the elongate body. A pushing forceis applied to the push tube and transmitted to the distal tip to pushthe distal end of the elongate body through vasculature and into oraround the heart (e.g., into the epicardium of the heart). A portion ofthe elongate body proximal to the distal tip and coupled thereto ispulled as the distal tip is pushed by the push tube. In another option,the distal tip includes a seat. The push tube and the seat include,optionally, non-circular perimeters or a key and a recess. The push tubeis rotated to correspondingly rotate the distal tip into a desiredorientation for optimum electrode to tissue contact, in one option. Inanother option, the push tube is rotated to turn the distal tip and theelongate body and allow for easier navigation of the vasculature.

Because the push tube is fed over the guide wire or over the elongatebody, a stylet lumen or the like is not necessary. In one option, theelongate body has a smaller cross-section and is less invasive thanleads having a stylet lumen. The lead assembly includes additionalconductors or the like in the space occupied by a stylet lumen, inanother option. The conductors of the lead assembly described hereininclude cables that extend substantially linearly along the elongatebody because a stylet lumen formed with coiled conductors is notnecessary. Linear cables take up less space within the elongate body, ascompared to coiled conductors, and allow for a lead assembly with asmaller outer perimeter that also has multiple conductors andcorresponding electrodes. In yet another option, a lumen is formedwithin the elongate body and is sized and shaped to receive the pushtube and the guide wire and the push tube is fed over the guide wire tonavigate the elongate body through vasculature. Having a push tube lumenwithin the elongate body decreases the profile of the elongate bodyallowing for easier navigation of the lead assembly. Additionally, thepush tube provides increased column strength compared to a stylet andfacilitates transmission of increased pushing forces to the distal endof the elongate body.

Moreover, the push tube of the assembly allows for the positioning of avariety of active fixation devices into desired orientations along theelongate body, for instance, after the elongate body is positionedwithin vasculature and/or a heart. The elongate body tracks through thevasculature easily without the active fixation devices disposed alongthe elongate body until after implantation of the elongate body. In oneoption, the active fixation devices have a larger profile than theelongate body and are introduced after the elongate body is positionedas desired within a heart and/or the vasculature. In another option,when the active fixation device and distal tip are coupled the combinedouter perimeter engages the surrounding vasculature of, for example, avein or artery, and securely couples the elongate body with thevasculature. In another option, active fixation devices sized and shapedto deform the elongate body are advanced along the elongate body. In oneoption, the active fixation devices deform and push the elongate body(e.g. including electrodes) into snug engagement with the vasculature.In another option, active fixation devices are actuated with the pushtube (e.g. by rotating the push tube to turn a threaded fixation device)to couple with surfaces within the vasculature or on the epicardialsurfaces of a heart.

These and other embodiments, aspects, advantages, and features of thepresent invention will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the art byreference to the following description of the invention and referenceddrawings or by practice of the invention. The aspects, advantages, andfeatures of the invention are realized and attained by means of theinstrumentalities, procedures, and combinations particularly pointed outin the appended claims and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating a lead constructed in accordance withone embodiment.

FIG. 2 is a detailed cross-sectional view illustrating a distal portionof a lead constructed in accordance with one embodiment.

FIG. 3 is a detailed cross-sectional view illustrating a distal tip of alead constructed in accordance with one embodiment.

FIG. 4A is a sectional view illustrating a distal tip of a leadconstructed in accordance with another embodiment.

FIG. 4B is a sectional view illustrating a distal tip of a leadconstructed in accordance with yet another embodiment.

FIG. 5 is a cross-sectional view illustrating a distal portion of a leadconstructed in accordance with one embodiment.

FIG. 6 is a cross-sectional view illustrating a guide wire and push tubeconstructed in accordance with another embodiment.

FIG. 7A is a side view illustrating a distal tip of a lead constructedin accordance with one embodiment.

FIG. 7B is a side view illustrating a distal tip of a lead constructedin accordance with another embodiment.

FIG. 8 is a detailed side view illustrating a push tube constructed inaccordance with one embodiment.

FIG. 9 is a detailed side view illustrating a push tube constructed inaccordance with another embodiment.

FIG. 10 is a cross-sectional view illustrating a lead constructed inaccordance with another embodiment.

FIG. 11 is a cross-sectional view illustrating a lead constructed inaccordance with yet another embodiment.

FIG. 12A is an end view illustrating a distal tip of a lead constructedin accordance with one embodiment.

FIG. 12B is an end view illustrating a distal tip of a lead constructedin accordance with another embodiment.

FIG. 12C is an end view illustrating a distal tip of a lead constructedin accordance with yet another embodiment.

FIG. 12D is an end view illustrating a push tube distal end of a pushtube constructed in accordance with one embodiment.

FIG. 13 is a side view illustrating a push tube and a distal tipconstructed in accordance with one embodiment.

FIG. 14 is a side view illustrating a distal portion of a lead and anactive fixation device constructed in accordance with one embodiment.

FIG. 15 is a sectional view illustrating a distal portion of a lead andan active fixation device constructed in accordance with anotherembodiment.

FIG. 16 is a detailed perspective view illustrating a portion of a leadand an active fixation device constructed in accordance with anotherembodiment.

FIG. 17A is a detailed side view of a portion of a lead and an activefixation device constructed in accordance with yet another embodiment.

FIG. 17B is a detailed side view of a portion of a lead and an activefixation device constructed in accordance with yet another embodiment.

FIG. 18A is a detailed side view of a portion of a lead and an activefixation device constructed in accordance with still another embodiment.

FIG. 18B is a detailed side view of a portion of a lead and an activefixation device constructed in accordance with still another embodiment.

FIG. 19A is a detailed side view of a portion of a lead and an activefixation device constructed in accordance with a further embodiment.

FIG. 19B is a detailed side view of a portion of a lead and an activefixation device constructed in accordance with a further embodiment.

FIG. 19C is a detailed side view of a portion of a lead and an activefixation device constructed in accordance with a further embodiment.

FIG. 19D is a detailed side view of a lead and an active fixation deviceconstructed in accordance with a further embodiment.

FIG. 19E is a side view of a lead and an active fixation device in afirst unexpanded position constructed in accordance with a furtherembodiment.

FIG. 19F is a side view of a lead and an active fixation device in asecond radially expanded position constructed in accordance with afurther embodiment.

FIG. 20 is a cross-sectional view of an active fixation device and apush tube constructed in accordance with another embodiment.

FIG. 21 is a detailed cross-sectional view of a portion of a lead and anactive fixation device and a push tube constructed in accordance withanother embodiment.

FIG. 22 is a detailed cross-sectional view of a portion of a lead and anactive fixation device and a push tube constructed in accordance withanother embodiment.

FIG. 23 is a sectional view of a push tube and an active fixation deviceconstructed in accordance with another embodiment.

FIG. 24 is a block diagram illustrating one method of implanting a lead.

DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and that structuralchanges may be made without departing from the scope of the presentinvention. Therefore, the following detailed description is not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims and their equivalents.

FIG. 1 is a side view of a lead assembly 100 including an elongate body102. The elongate body 102 extends between a distal end 104 and aproximal end 106. The elongate body includes a connector terminal 108 atthe proximal end 106. The connector terminal 108 is sized and shaped tocouple with a pulse generator, for example, an implantable defibrillatoror pacemaker. The distal end 104 includes at least one electrode 112which electrically couples the lead assembly 100 with a heart. Inanother option, the electrode 112 can be a unipolar or multipolar typeelectrode. In still another option, multiple electrodes 112 are providedon the elongate body 102. At least one electrical conductor 110, asshown in phantom lines in FIG. 1, is disposed within the elongate body102. The at least one electrical conductor 110 electrically couples theelectrode 112 with the connector terminal 108 of the lead assembly 100.In another option, the lead assembly 100 includes multiple conductors110 electrically coupled to multiple corresponding electrodes 112.

In one option, the elongate body 102 includes an insulating layer 114formed of a biocompatible polymer suitable for implantation within thehuman body. The insulating layer 114 is made from a silicone rubber typepolymer, in one option. In another option, the insulating layer 114includes polyurethane. In yet another option, the insulating layer 114includes polyethylene terephthalate (PTFE). In still another option, theinsulating layer 114 includes ethylene-tetrafluoroethylene (ETFE), orpolysiloxane urethane. The insulating layer includes other biocompatiblepolymers, optionally. The insulating layer 114 surrounds and insulatesthe conductor 110.

As shown in FIGS. 1 and 2, the lead assembly 100 includes a distal tip116 coupled substantially adjacent to the distal end 104 of the elongatebody 102. The distal tip 116 is securely coupled to the elongate body102 to prevent relative movement, such as rotation therebetween. In oneoption, the distal tip 116 is adhered to the elongate body 102. Thedistal tip 116 is integral with the elongate body 102, in anotheroption. Optionally, the distal tip 116, includes, but is not limited topolymers such as polyurethane, silicone rubber, polyetheretherketone, orthe like. In one option, the distal tip includespolytretrafluoroethylene and/or ethylene tetrafluoroethylene for lowfriction. In another option, the distal tip includes a lubriciouscoating (e.g. a polyethylene glycol hydrophilic coating). In yet anotheroption, the distal tip 116 is coupled to the elongate body 102 with aninterference fit. In one option, the electrode 112 is coupled to thedistal tip 116. The conductor 110, in another option, correspondinglyextends into the distal tip 116 to couple with the electrode 112.

In one option, the lead assembly 100 includes an active fixation device120 slidably coupled around the elongate body 102. The active fixationdevice 120 is sized and shaped, in another option, to engage againstvasculature around a heart and immobilize at least a portion of the leadassembly 100. In yet another option, the lead assembly 100 includes apush tube 122 sized and shaped to couple with the active fixation device120. The push tube 122 operates to translate the active fixation device120 along the elongate body 102. In yet another option, the push tube122 is sized and shaped to couple with the distal tip 116. Translationof the push tube 122 is transmitted to the distal tip 116 and the distaltip 116 correspondingly advances the lead assembly 100 throughvasculature, such as the tortuous vasculature around the left side of aheart. The push tube 122 includes, but is not limited to, a tube, a tubeintegral to the elongate body, a catheter, or the like.

In another option, the distal tip 116 includes a side rail seat 118.Referring now to FIG. 2, the side rail seat 118 includes, in yet anotheroption, a guide wire lumen 200 sized and shaped to receive a guide wire202. The guide wire 202, optionally extends along the elongate body 102and through vasculature to a desired location for implantation of thedistal end 104 of the lead assembly 100. The guide wire 202 is slidablycoupled with the inner surface of the side rail seat 118 that definesthe guide wire lumen 200. In another option, at least one of the guidewire 202 and the surface defining the guide wire lumen 200 includes alubricious coating to facilitate movement between the guide wire 202 andthe side rail seat 118. The lubricious coating includes, but is notlimited to polyethylene glycol, silicone oils, fluoropolymers or thelike. In one example, the lubricious coating includes SILGLIDE® aregistered trademark of Applied Membrane Technology, Inc.

The lead assembly 100 includes the push tube 122, slidably coupledaround the guide wire 202, optionally. The push tube 122 is a tubularmember, in one option. In another option, the push tube 122 has an innerperimeter corresponding to the guide wire 202. The push tube 122includes various cross sectional geometries, in yet another option. Forexample, the push tube 122 has a circular, square, ovular, triangulargeometry or the like. In another example, the push tube 122 has varyingcross-sectional geometries along different portions of the push tube122. Non-circular geometries allow for transmission of rotation to thedistal tip 116 optionally, as described below. The push tube 122, in oneoption, extends along the elongate body 102. In one example, the pushtube 122 is substantially adjacent (e.g., juxtaposed) to the elongatebody 102. In another option, the push tube 122 extends from at least theproximal end 106 (FIG. 1) of the elongate body 102 to the distal end104. In one option, at least one of the guide wire 202 and the push tube122 includes a lubricious coating to facilitate slidable movementbetween the guide wire 202 and the push tube 122. The push tube 122includes a push tube distal end 206 sized and shaped to couple with theside rail seat 118.

The push tube 122, in one option, includes a material that providessufficient column strength to transmit force along the push tube 122 tothe side rail seat 118 and the distal tip 116. Optionally, the push tube122 is constructed with a kink-resistant material to substantiallyeliminate kinks along the push tube 122 that prevent transmission ofpushing forces along the entirety of the push tube 122. In anotheroption, the push tube 122 is constructed with a flexible materialcapable of bowing and snaking through vasculature to track with theelongate body 102 during navigation of vessels. In yet another option,the push tube 122 is constructed with a material capable of transmittingrotational force along the push tube 122 to the side rail seat 118 andthe distal tip 116. The push tube 122, in one example, includes, but isnot limited to a super elastic material, such as Nitinol. In anotherexample, the push tube 122 includes stainless steel. In yet anotherexample, the push tube 122 includes a polymer, metal, composite (e.g.polymer with a metal braiding), or the like. Optionally, the push tube122 has at least one of a coiled, slotted tube, varying wall thickness,stent-like tube and/or a tubular cable construction (i.e. a plurality ofadjacent cables) to provide the push tube 122 with a desired stiffnessor durometer for snaking through vasculature.

FIG. 3 is a cross sectional view showing the distal tip 116 of the leadassembly 100 and the push tube distal end 206. In one option, the pushtube distal end 206 includes a recess 300. The side rail seat 118includes a corresponding key 302 sized and shaped to engage with thepush tube distal end 206. In another option, the push tube distal end206 includes a key and the side rail seat 118 includes a recess. Therecess 300 and key 302 cooperate to prevent rotation of the push tube122 relative to the side rail seat 118 and the distal tip 116. In oneoption, rotation of the push tube 122 is transmitted at the push tubedistal end 206 to the side rail seat 118 through cooperation of the key302 and the recess 300. Rotation of the push tube 122, in anotheroption, correspondingly rotates the side rail seat 118 and the distaltip 116. Optionally, rotation of the distal tip 116 twists the leadassembly 100 including the elongate body 102 into a variety oforientations and aids in navigating the lead assembly 100 throughtortuous vasculature including, for instance, snags, sharp corners andthe like. In one option, the distal tip 116 includes materialssufficiently rigid (e.g. stainless steel or polyetheretherketone) totransmit rotation of the push tube 122 through the side rail seat 118 tothe elongate body 102. In another option, the distal tip 116 includes adeformable material such as silicone rubber, and a brace 304 extendsbetween the side rail seat 118 and the elongate body 102 to transmitrotation of the push tube 122 to the elongate body 102 of the leadassembly 100.

FIGS. 4A and 4B show examples of non-circular geometries for the pushtube distal end 206 and the side rail seat 118. The inner surface of theside rail seat 118 shown in FIG. 4A includes a square geometry. The pushtube distal end 206, in one option has an outer perimeter including acorresponding square geometry. The square push tube distal end 206 andcorresponding side rail seat 118 cooperate to prevent relative rotationbetween the push tube distal end 206 and the side rail seat 118. Inanother option, the push tube distal end 206 and the inner surface ofthe side rail seat 118 have other non-circular geometries, for instance,triangular or ovular geometries or the like. Optionally, the distal tip116 includes a plurality of side rail seats 118 to enhance steerabilityof the lead assembly 100.

The push tube distal end 206 shown in FIG. 4B has a substantiallycircular outer perimeter. In one option, the push tube distal end 206includes ears 400. The ears 400 are disposed within correspondinggrooves 402 within the side rail seat 118. The ears 400 engage with theinner surface of the side rail seat 118 that defines the grooves 402 toprevent relative rotation between the push tube distal end 206 and theside rail seat 118. Optionally, rotation of the push tube 122 (FIG. 2)with a non-circular geometry and/or ears 400 is transmitted to the siderail seat 118 and the distal tip 116 (FIG. 1) to twist the lead assembly100 into various orientations.

FIG. 5 is a detailed cross sectional view of the lead assembly 100including the distal tip 116 having the side rail seat 118. The siderail seat 118 includes, in one option, a socket 500 sized and shaped toreceive the push tube distal end 206 of the push tube 122. The socket500 is optionally concentric with the guide wire lumen 200. In anotheroption, an inner perimeter 502 of the side rail seat 118 that definesthe socket 500 is sized and shaped to snugly couple with the push tubedistal end 206 and immobilizes the push tube distal end 206 with respectto the distal tip 116 and the side rail seat 118. In one option, thepush tube distal end 206 is securely coupled to the side rail seat 118to substantially prevent undesired uncoupling of the push tube 122 fromthe side rail seat 118 during, for instance, exchange of guide wires202. In another option, the push tube distal end 206 is securely coupledto the side rail seat 118 to substantially prevent uncoupling betweenthe push tube 122 and the side rail seat 118 when the push tube 122 isoptionally pulled toward the proximal end 106 of the elongate body 102(FIG. 1) during navigation of the lead assembly 100.

In one option, the push tube distal end 206 includes an outer perimeter504 slightly larger than the inner perimeter 502 of the side rail seat118 that defines the socket 500. At least the push tube distal end 206is optionally deformable and engages with the side rail seat 118 to forman interference fit between the push tube distal end 206 and the siderail seat 118. In another option, the outer perimeter 504 of the pushtube distal end 206 includes an expandable material, such as a hydrogelor the like. The outer perimeter 504 expands from exposure to water(i.e. during implantation) and engages the inner perimeter 502 thatdefines the socket 500 when the push tube distal end 206 is disposedwithin the socket 500. In yet another option, at least one of the innerperimeter 502 of the side rail seat 118 and the outer perimeter 504 ofthe push tube distal end 206 includes an expandable material to securelycouple the push tube 122 with the distal tip 116 and the side rail seat118.

FIG. 6 is a detailed cross sectional view of the push tube 122 and thedistal tip 116 including the side rail seat 118. The side rail seat 118includes a deformable coil 600, in one option. The deformable coil 600is disposed, at least partially in another option, within the socket 500and defines a portion of the inner perimeter 502. In yet another option,the deformable coil 600 extends along the socket 500 and at least aportion of the deformable coil 600 surrounds the guide wire 202.Optionally, a portion of the deformable coil 600 extends into the guidewire lumen 200. The deformable coil 600 is sized and shaped to deformwhen the push tube 122 is received within the socket 500. In one option,the push tube 122 engages against the inner perimeter 502 of the socket500 including the deformable coil 600 and forces the deformable coil 600away from the guide wire 202. Deformation of the deformable coil 600 bythe push tube 122 creates a restoring force within the deformable coil600. The restoring force acts on the deformable coil 600 to tighten thedeformable coil 600 around the push tube distal end 206, in anotheroption. The deformable coil 600 is prevented from assuming theundeformed shape and snugly grasps and immobilizes the push tube distalend 206, in yet another option. As described above, the push tube distalend 206 is securely coupled to the side rail seat 118 to substantiallyprevent undesired uncoupling of the push tube 122 from the side railseat 118 during, for instance, exchange of guide wires 202.

FIGS. 7A and 7B are side views illustrating the guide wire 202 disposedwithin the side rail seat 118 of the distal tip 116. In one option, thedistal tip 116 has a proximal portion 700 and a distal portion 702 andthe proximal portion 700 has an outer perimeter 704 larger than an outerperimeter 706 of the distal portion 702. In another option, the distaltip 116 is tapered from the proximal portion 700 toward the distalportion 702. Tapering of the distal tip 116 gradually increases the sizeof the lead assembly 100 between the distal end 104 and the proximal end106 (FIG. 1) to incorporate the guide wire 202 and the push tube 122extending along the elongate body 102. The push tube 122, guide wire 202and the accompanying side rail seat 118 thereby easily track with theelongate body 102 (FIG. 1) through vasculature, such as the coronaryveins. The taper of the distal tip 116 reduces snagging of the distaltip 116 within vasculature and facilitates moving the lead assembly 100around corners and bends within vessels.

In another option, shown in FIG. 7A, the guide wire lumen 200 extendsthrough the distal tip 116 at an oblique angle θ such that the guidewire 202 extends through the side rail seat 118 at a slant relative tothe distal end 104 of the elongate body 102. The guide wire 202 exitsthe side rail seat 118 at the oblique angle θ of the guide wire lumen200. In yet another option, the guide wire 202 and the push tube 122 aredeformable and extend from the side rail seat 118 to the proximal end106 substantially adjacent to the elongate body 102. The oblique angle θis optionally measured along a line 708 substantially parallel to thelongitudinal axis 710 of the elongate body 102 distal end 104. Theoblique angle θ, in another option is inclined relative to thelongitudinal axis 710 of the elongate body 102 distal end 104. The guidewire lumen 200 with the oblique angle θ, in one option, provides anangled track for the guide wire 202 to improve tracking of the leadassembly 100 through tortuous vasculature, for instance, coronary veins.In another option, the oblique angle θ allows the lead assembly 100 totrack around corners and avoid snags within the vessels.

In yet another option, shown in FIG. 7B, the guide wire lumen 200extends through the distal tip 116 at an oblique angle α such that theguide wire 202 extends through the side rail seat 118 at a decliningslant relative to the longitudinal axis 710 of the elongate body 102distal end 104. The guide wire 202 exits the side rail seat 118 at theoblique angle α of the guide wire lumen 200. The oblique angle α isoptionally measured along a line 708 substantially parallel to thelongitudinal axis 710 of the elongate body 102 distal end 104. The guidewire lumen 200 with the oblique angle α, in one option, provides anangled track for the guide wire 202 to improve tracking of the leadassembly 100 through tortuous vasculature including, for example,corners, snags and the like.

In still another option, the distal tip 116 is constructed with, but notlimited to, a deformable material such as silicone rubber or the like,described above. In one option, pushing the deformable distal tip 116with the push tube 122 facilitates navigation of the lead assembly 100around corners and snags as the distal tip 116 deforms to fit around thecorners and/or through tight spaces. In another option, the distal tipincludes a combination of the tapered distal tip 116, the oblique anglesθ or α, and the distal tip 116 constructed with a deformable material tofurther enhance the tracking of the lead assembly 100 through vessels.

FIG. 8 is a detailed side view of the push tube distal end 206. In oneoption, the push tube distal end 206 includes a flexible feature 800.The flexible feature 800 enhances the flexibility of the push tube 122at the push tube distal end 204 to facilitate bending of the leadassembly 100 at the distal tip 116, in another option. The flexiblefeature 800, in one option, includes at least one groove 802 extendingat least part way around the push tube 122. The groove 802 extendsbetween the outer perimeter 804 of the push tube 122 and the innerperimeter 806 of the push tube 122, in one option. In another option,the groove 802 is scored into the outer perimeter 804 and extendsbetween the outer perimeter 804 and an intermediate portion of the pushtube 122 between the outer perimeter 804 and the inner perimeter 806. Asshown in FIG. 8, in one option, the groove 802 helically extends aroundthe push tube distal end 206 to form a spiral. The groove 802 is formedin the push tube distal end 206 by machining, laser machining, chemicaletching or the like.

A strut 808 extends across the groove 802, in another option, to providecolumn strength to the push tube distal end 206 for axial forcedelivered to the side rail seat 118 and the distal tip 116 (See FIG. 1).In one option, the strut 808 is formed out of the push tube 122 duringformation of the groove 802. In another option, the strut 808 is coupledto the outer perimeter 804 or inner perimeter 806 of the push tube 122.Optionally, multiple grooves 802 are formed in the push tube distal end206 to provide the flexible feature 800. In yet another option, theflexible features 800 are formed along other portions of the push tube122 to provide increased flexibility at various positions on the pushtube 122 for enhanced navigation through vasculature.

FIG. 9 is a detailed side view of the push tube distal end 206 showinganother example of the flexible feature 800. The flexible feature 800,in one option is a thin wall section 900 of the push tube distal end206. The inner perimeter 806 of the push tube 122 is machined, etched orthe like (described above), to form the thin wall section 900, inanother option. In yet another option, the push tube 122 is molded toinclude the push tube distal end 206 with the thin wall section 900.Optionally, the thin wall section 900 is formed on the outer perimeter804 of the push tube distal end 206. The thin wall section 900 providesadditional flexibility to the push tube distal end 206 to aid innavigating the distal tip 116 of the lead assembly 100 (FIG. 1) throughtortuous vasculature. With a metal push tube 122 (e.g., Nitinol), in oneoption, the wall thickness is between around 0.001 and 0.003 inches andthe thin wall section 900 is between around 0.002 and 0.0005 inchesthick. Where the push tube 122 includes polymers, optionally, the thinwall section 900 has a thickness around 0.0005 inches. The flexiblefeature 800, in another option includes at least one of a coiled,slotted tube, varying wall thickness, stent-like tube and/or a tubularcable construction (i.e. a plurality of adjacent cables) to provide theflexible feature 800 with a desired stiffness or durometer for snakingthrough vasculature.

Referring again to FIG. 2, in operation, the guide wire 202 is fed intothe vasculature toward a desired location. The side rail seat 118, inone option, is coupled to the guide wire 202 with the guide wire 202disposed in the guide wire lumen 200. The push tube 122 is slidablycoupled to the guide wire 202 and moved down the guide wire 202 towardthe side rail seat 118 and the distal tip 116. The distal tip 116including the side rail seat 118, in one option, is sized and shaped tocouple with the push tube distal end 206. The push tube distal end 206couples with the distal tip 116. In one option, the push tube distal end206 is received in a socket 500 (FIG. 5) sized and shaped to snuglycouple and immobilize the push tube distal end 206, as described above.An axial pushing force is applied to the push tube 122 and transmittedalong the push tube to the distal tip 116 including the side rail seat118, in another option. The pushing force applied to the distal tip 116operates to pull the lead assembly 100 proximal to the distal tip 116through vessels. The push tube 122 is therefore used, in one option, tonavigate the lead assembly 100 through vasculature. The push tube 122facilitates the use of narrow flexible leads, in one option, as the pushtube 122 is moved over the guide wire 202 and engaged against the siderail seat 118 to navigate the flexible leads. A stylet is unnecessarywith the push tube 122. Additionally, the tubular geometry of the pushtube 122 provides increased column strength to enhance transmission ofthe pushing force to the distal tip 116 compared to, for example, astylet.

Referring now to FIG. 8, the push tube 122 includes a flexible feature800, in one option. The flexible feature 800 allows the push tube distalend 206 to bend and correspondingly snake the side rail seat 118 and thedistal tip 116 around corners or the like. In another option, theflexible feature 800 is positioned along the push tube 122 at variouslocations and improves the flexibility of the push tube 122 at thelocations to improve tracking of the lead assembly 100 through tortuousvasculature.

In another option, shown in FIG. 3, at least one of the side rail seat118 and the push tube distal end 206 include a recess 300 and acorresponding key 302. The push tube 122 is rotated, optionally, andtransmits the rotation to the distal tip 116 and the side rail seat 118by the recess 300 and the key 302. The lead assembly 100 twists with thedistal tip 116. Twisting of the lead assembly improves the tracking ofthe lead assembly 100 around corners, snags or the like in vasculature.In yet another option, the push tube distal end 206 and the innersurface of the side rail seat 118 include corresponding non-circulargeometries or ears 400 (FIGS. 4A and 4B) to transmit rotation of thepush tube 122 to the distal tip 116 and the lead assembly 100.

In still another option, the guide wire 202 exits the side rail seat 118at an oblique angle (e.g., θ or α) corresponding to an oblique angle ofthe guide wire lumen 200 as shown in FIGS. 7A and 7B. The lead assembly100 follows the slanted path of the guide wire 202 through thevasculature as it is pushed over the guide wire 202 with the push tube122, in one option. The slanted path of the guide wire 202 provides anangled track, in another option, for the lead assembly 100 to followaround corners, snags or the like.

FIG. 10 is a cross section view of a lead assembly 1000. The leadassembly 1000 is similar in some respects to the lead assembly 100 (FIG.1), described above. The lead assembly 1000 includes an elongate body1002 extending from a proximal end 1006 to a distal end 1004. In thelead assembly 1000 shown in FIG. 10, at least one conductor 1008 extendsfrom the proximal end 1006 to a location substantially adjacent to thedistal end 1004. In one option, the conductor 1008 is coiled within theelongate body 1002 and forms a lead lumen 1010 sized and shaped toreceive a guide wire 1012 and a push tube 1014. The lead assembly 1000is coupled around the guide wire 1012 when the guide wire 1012 isdisposed in the lead lumen 1010. In another option, the lead lumen 1010is sized and shaped to receive the push tube 1014 without the guide wire1012. The conductor 1008, optionally, is electrically coupled to anelectrode 1009 adjacent to the distal end 1004.

The lead assembly 1000 includes, in another option, a distal tip 1016.The distal tip 1016 includes, optionally, a guide wire lumen 1018. Theguide wire 1012 is sized and shaped to pass through the guide wire lumen1018 and slidably couple with the inner surface 1020 defining the guidewire lumen 1018. The guide wire 1012 extends through the lead lumen 1010and guide wire lumen 1018.

In another option, the distal tip 1016 includes a seat 1022 sized andshaped to receive a push tube distal end 1024. Prior to engagement withthe seat 1022, the push tube 1014 is slidably coupled with the elongatebody 1002. The seat 1022, in one option, grasps and immobilizes the pushtube distal end 1024 as described above with the socket 500 (FIG. 5).Optionally, the push tube distal end 1024 is securely coupled to thedistal tip 1016 to substantially prevent undesired uncoupling of thepush tube 1014 from the distal tip during, for instance, exchange ofguide wires 1012 or navigation of the lead assembly 1000. In anotheroption, the seat 1022 provides a transition between the lead lumen 1010and the guide wire lumen 1018. The push tube distal end 1024 engagesagainst the seat 1022 and is prevented from entering the narrower guidewire lumen 1018, in yet another option. Pushing forces applied along thepush tube 1014 are transmitted to the distal tip 1016 through engagementof the seat 1022 and the push tube distal end 1024. In one option, thepush tube 1014 operates to push the distal tip 1016 and correspondinglypull the elongate body 1002 over the guide wire 1012. Optionally, thepush tube 1014 is slidably coupled around the guide wire 1012 to allowthe push tube 1014 and the elongate body 1002 coupled around the pushtube 1014 to pass over the guide wire 1012.

In operation, a pushing force applied along a longitudinal axis of thepush tube 1014 is transmitted to the seat 1022 and distal tip 1016through engagement of the push tube distal end 1024 and the seat 1022.In one option, as the distal tip 1016 receives the pushing force throughthe push tube 1024, the elongate body 1002 proximal the distal tip 1016is correspondingly pulled through the vasculature. In another option,the lead assembly 1000 passes over the guide wire 1012 and navigatesvasculature as the push tube 1024 pushes the distal tip 1016 andcorrespondingly pulls the elongate body 1002. In yet another option,where the lead assembly does not include a guide wire 1012, the pushtube 1024 transmits pushing forces to the seat 1022 and the distal tip1016 to navigate the lead assembly 1000 through vasculature. The tubulargeometry of the push tube 1024 provides increased column strengthcompared to, for instance, a stylet and facilitates navigation of thelead assembly in tortuous vessels.

FIG. 11 is a sectional view of a lead assembly 1100 including an activefixation device 1102. The active fixation device 1102 includesthreading, helically wound helix projections or the like. The leadassembly 1100 includes an elongate body 1104 extending from a proximalend 1106 to a distal end 1108. The elongate body includes a conductor1110 extending, in one option, from the proximal end to the distal end1108. The conductor 1110 is surrounded, in another option, by aninsulating layer 1112. The insulating layer 1112, optionally, is similarto the insulating layer 114 of the lead assembly 100. In another option,the insulating layer 1112 includes a distal portion 1114 where theinsulating layer 1112 narrows toward the distal end 1108 to provideincreased flexibility for bending of the lead assembly 1100. Optionally,the distal portion 1114 is sufficiently flexible for the distal portion1114 to bend at least 90 degrees around the active fixation device 1102.

A distal tip 1116 is coupled to the elongate body 1104 substantiallyadjacent to the distal end 1108. In one option, the conductor 1110 iselectrically coupled to the distal tip 1116. The conductor 1110, in oneexample, is welded, soldered or bondied to the distal tip 1116. Inanother example, the distal tip 1116 is crimped, staked or swaged aroundthe conductor 1110. In one option, the distal tip 1116 includes theactive fixation device 1102. In another option, the active fixationdevice 1102 is electrically coupled to the distal tip 1116, for instancethe active fixation device 1102 is integral to the distal tip 1116. Inanother option, the distal tip 1116 and the active fixation device 1102are constructed with conductive metal and coupled with each other.

In one option, the distal tip 1116 includes a seat 1118 sized and shapedto receive a push tube distal end 1122 of a push tube 1120. The seat1118 includes, in another option, an outer perimeter 1124 sized andshaped to snugly couple with the inner perimeter 1126 of the push tubedistal end 1122. The push tube 1120 is slidably coupled around theelongate body 1104, in one option. In another option, the push tubedistal end 1122 engages against the seat 1118 so pushing force appliedto the push tube 1120 is transmitted through the push tube distal end1122 and the seat 1118 to the distal tip 1116. Optionally, the push tube1120 is operated to push the distal tip 1116 onto the surface 1128, forinstance the epicardium of a heart. Pushing the distal tip 1116 onto thesurface 1128 couples the active fixation device 1102 to the surface 1128and securely fastens the lead assembly 1100 to the surface 1128, inanother option. The push tube 1120 has sufficient column strength toengage the distal tip 1116 against the surface 1128. In one example, thepush tube 1120 is constructed with a super-elastic metal, such asNitinol. In another example, the push tube 1120 includes stainlesssteel. In yet another example, the push tube 1120 includes, but is notlimited to, a polymer, metal, a composite (e.g., polymer tube includingbraided metal) or the like.

In another option, the distal tip 1116 includes a radially extendingflange 1130. In one example, the flange 1130 extends substantiallyaround the distal tip 1116. In another example, the flange 1130 extendsaround a portion of the distal tip 1116. In one option, the flange 1130is electrically coupled to the conductor 1110 through the distal tip1116 and serves as an electrode to provide electrical stimulation to thesurface 1128 (e.g., the epicardium of the heart). In another option, theflange 1130 engages against a surface 1128 during insertion of theactive fixation device 1102 and acts as a depth stop to prevent deeperinsertion of the active fixation device 1102 into the surface 1128. Theflange 1130 includes, but is not limited to, a biocompatible platinumand iridium or titanium screen mesh that promotes tissue ingrowth, inone option. In another option, the flange 1130 is constructed with, butnot limited to, a polymer fiber mesh including, for instance, polyesterand/or polyethylene terephthalate. Optionally, the flange 1130 includesDACRON®, a registered trademark of E.I. du Pont de Nemours and Company.

In yet another option, the seat 1118 includes a tapered mouth 1132 thatsubstantially surrounds the elongate body 1104 as it extends into thedistal tip 1116. In one option, the tapered mouth 1132 is providedaround the elongate body 1104 to decrease abrasion of the insulatinglayer 1112 and provide a gentle slope for the elongate body 1104 to bendagainst after implantation of the lead assembly 1100. The tapered mouth1132, in another option, substantially prevents the elongate body 1104from sharply bending at the seat 1118 and thereby decreases wear on theconductor 1110 due to sharp bending.

FIGS. 12A-C are views of examples of the distal tip 1116 showing theouter perimeter 1124 of the seat 1118. FIG. 12A shows a distal tip 1116including a seat having a substantially circular outer perimeter 1124.At least one exit groove 1200 extends from the outer perimeter 1124toward the elongate body 1104, in one option. The exit grooves 1200, inanother option, are sized and shaped to snugly receive and immobilize atleast a portion of the elongate body 1104. In one option, the elongatebody 1104 is bent into the exit groove 1200 after coupling the distaltip 1116 with the surface 1128 (e.g. the epicardium of the heart). Theelongate body 1104 is slightly larger than the exit groove 1200 anddeforms when pressed into the exit groove 1200. The portion of the seat1118 surrounding the elongate body 1104 engages against the elongatebody 1104 to grasp and immobilize the elongate body 1104.

In another option, the exit groove 1200 acts as a recess for engagementwith a corresponding key 1202 on the push tube distal end 1122 (See FIG.12D). As shown in the end view of FIG. 12D, in one option, the key 1202is sized and shaped to fit within the exit groove 1200 of the distal tip1116. In another option, the seat 1118 includes the key and the pushtube distal end 1122 includes the recess. In yet another option, the key1202 and the exit groove 1200 cooperate to substantially preventrelative rotation between the distal tip 1116 and the push tube 1120.Optionally, rotation of the push tube 1120 is transmitted to the distaltip 1116 and to the active fixation device 1102 (FIG. 11) by cooperationof the key 1202 with the seat 1118. The push tube 1120 operates, in oneoption, to drive the active fixation device 1102 (including for example,threading or a helix projection) into the surface 1128 (FIG. 11) throughrotation of the distal tip 1116.

FIG. 128 is an end view of another example of distal tip 1116 includinga non-circular outer perimeter 1124 for the seat 1118, such as an ovulargeometry. In another example, the seat 1118 includes a square outerperimeter 1124 as shown in FIG. 12C. In yet another example, the outerperimeter 1124 of the seat 1118 is triangular, rectangular or the like.The push tube 1120 includes a corresponding non-circular push tubedistal end 1122 sized and shaped to couple with the seat 1116 (See FIG.11). Rotation of the push tube 1120 is transmitted to the distal tip1116 and to the active fixation device 1102 by cooperation of thenon-circular push tube distal end 1122 with the correspondingnon-circular seat 1118. The push tube 1120 operates, in one option, todrive the active fixation device 1102 into the surface 1128 (FIG. 11)through rotation of the distal tip 1116. In another option, the seats1118 shown in FIGS. 12B and 12C include exit grooves 1200 sized andshaped to grasp and immobilize the elongate body 1104.

In operation, the push tube 1120 is slidably coupled around the elongatebody 1104 and moved toward the distal tip 1116. As shown in FIG. 11, thepush tube distal end 1122 is engaged against the seat 1118 of the distaltip 1116. As described above, in one option, the non-circular innerperimeter 1126 of the push tube distal end 1122 couples around thecorresponding outer perimeter 1124 of the seat 1118 to transmit rotationof the push tube 1120 to the distal tip 1116 and the active fixationdevice 1102 (See FIGS. 11, 12B, 12C). In another option, shown in FIG.12D, the push tube distal end 1122 includes a key 1202 sized and shapedto fit within the exit groove 1200. The key 1202 engages with the seat1118 to transmit rotation of the push tube 1120 to the distal end 1116and the active fixation device 1102 (See FIGS. 12A, 12D). Rotation ofthe active fixation device 1102 drives the device 1102 into the surface1128, such as the epicardium of a heart. In one option, the flange 1130engages against the surface 1128 during rotation of the active fixationdevice 1102 and acts as a depth stop to prevent deeper insertion of theactive fixation device 1102 into the surface 1128.

In one option, the active fixation device 1102 is electrically coupledto the conductor 1110 through the distal tip 1116. Coupling of theactive fixation device 1102 with the surface 1128 electrically couplesthe lead assembly 1100 with the surface 1128, optionally. In anotheroption, electrical stimulation is provided to the surface 1128 throughthe active fixation device 1102. In another option, the flange 1130 iselectrically coupled to the conductor 1110 through the distal tip 1116and electrical stimulation is provided to the surface 1128 through theflange 1130.

In another option, after the active fixation device 1102 couples thelead assembly 1100 with the surface 1128 the push tube 1120 is pulledaway from the distal tip 1116 and the push tube distal end 1122disengages from the seat 1118. In one option, the elongate body 1104 islapped up against the surface 1128 to minimize wear on the lead assembly1100 caused by, for example, chronic bending of the elongate body 1104experienced during beating of a heart. As shown in FIG. 13, in anotheroption, the push tube distal end 1122 sweeps the elongate body 1104 intothe exit groove 1200 to immobilize the elongate body 1104 and lap thebody 1104 against the surface 1128. Optionally, the push tube 1120 isuncoupled from the elongate body 1104 by pulling the push tube 1120 overthe elongate body 1104 toward the proximal end 1106. In another option,the push tube 1120 is sized and shaped to split and peel away from theelongate body 1104 when withdrawn toward the proximal end 1106.

FIG. 14 is a side view of the lead assembly 100 including one example ofan active fixation device 1400 used for, but not limited to, fixating alead in a coronary vessel. In one option, the active fixation device1400 includes a lumen 1402 sized and shaped to receive the guide wire202. In another option, the active fixation device 1400 is slidablycoupled around the guide wire 202. A guide projection 1404 extends fromthe active fixation device 1400, in yet another option. The guideprojection 1404, in one option extends around the elongate body 102 andis slidably coupled to the elongate body 102. In another option, theguide projection 1404 extends at least part way around the elongate body102. The guide projection 1404 and the lumen 1402 cooperatively ensurethe active fixation device 1404 moves along the elongate body 102 andthe guide wire 202, respectively. The push tube 122, optionally, engagesagainst the active fixation device 1404 and moves the device 1404 alongthe guide wire 202 toward the distal tip 116. In another option, thepush tube 122 is slidably coupled around the guide wire 202.

In another option, the active fixation device 1400 includes a rack 1406of teeth 1408. The teeth 1408 are bent back along the active fixationdevice 1400 and point toward the proximal end 106 (FIG. 1) of theelongate body 102, in one option. An engagement surface 1410 of thedistal tip 116 includes at least one pawl 1412 sized and shaped toengage against the teeth 1408 of the rack 1406. As shown in FIG. 14, inanother option, the engagement surface 1410 includes multiple pawls1412. In yet another option, the pawl 1412 points in an oppositedirection from the teeth 1408. The teeth 1408 are sized and shaped toallow movement of the active fixation device 1400 over the guide wire202 toward the distal tip 116. The teeth 1408, in one option, couple theactive fixation device 1400 to the distal tip 116 by coupling with thepawl 1412. Because of the orientation of the pawl 1412 and the teeth1408 of the rack 1406, the active fixation device 1400 is substantiallyprevented from moving away from the distal tip 116 when coupled to thedistal tip 116, in another option. The pawl 1412 and the teeth 1408cooperate to allow one-way movement of the active fixation device 1400toward the distal end 104 once the device 1400 is coupled to the distaltip 116.

In yet another option, the active fixation device 1400 has a first outerperimeter 1414 and the distal tip 116 has a second outer perimeter 1416.Coupling the active fixation device 1400 with the distal tip 116(described above) creates a combined outer perimeter that is larger thanthe first outer perimeter 1414 or the second outer perimeter 1416. Thecombined outer perimeter of the active fixation device 1400 and thedistal tip 116, in one option, wedges at least the distal end 104 of thelead assembly 100 within a vessel, described below. Optionally, theouter perimeter of the active fixation device 1400 gradually increasestoward the proximal end of the device 1400 to enhance engagement of thelead assembly 100 within a vessel. In another option, the activefixation device 1400 includes a textured surface 1418 sized and shapedto engage with the tissue of a vessel and couple the active fixationdevice 1400 and the lead assembly 100 to the vessel. The texturedsurface 1418, optionally, is sized and shaped to permit blood flowaround the distal tip 116. The textured surface 1418 includes, forexample, ridges, knurling, tines, mesh material, slots, holes or thelike. In another example, the textured surface 1418 is porous andpromotes tissue ingrowth to securely couple the active fixation device1400 to the vessel. In one option, the textured surface 1418 extendssubstantially around the active fixation device 1400. Optionally, theactive fixation device 1400 is constructed with a biocompatible materialincluding, but not limited to, silicone rubber, polyurethane,polyetheretherketone (PEEK), ethylenetetrafluoroethylene (ETFE),titanium, or the like. In another option, the active fixation device1400 is radio opaque.

In one option, the active fixation device 1400 is coupled to the distaltip 116 after positioning the lead assembly 100 in a desired location inthe vasculature. The active fixation device 1400 is moved along theguide wire 202, in another option, with the push tube 122. In yetanother option, the guide projection 1404 and guide wire 202 cooperateto ensure the active fixation device 1400 is aligned with the distal tip116 to allow secure coupling between the distal tip 116 and the activefixation device 1400. The push tube 122 moves the active fixation device1400 into engagement with the distal tip 116. The pawl 1412 and theteeth 1408 of the rack 1406 engage to securely couple the activefixation device 1400 to the distal tip 116. In one option, the pawl 1412and the teeth 1408 substantially prevent movement of the active fixationdevice 1400 away from the distal tip 116 toward, for instance, theproximal end 106 (FIG. 1) of the elongate body 102. The push tube 122positions the active fixation device 1400 where desired along the distaltip 116 and the pawl 1412 and the rack 1406 securely couple the device1400 in the desired position.

In another option, once the lead assembly 100 is positioned withinvasculature the active fixation device 1400 operates to securely couplethe lead assembly 100 to surrounding tissue to substantially preventdislodgement of the lead assembly 100. The combined outer perimeter ofthe active fixation device 1400 and the distal tip 116, in one option,is greater than the outer perimeter 1416 of the distal tip 116. Inanother option, when the active fixation device 1400 engages against thedistal tip 116 and is coupled thereto (described above), the combinedouter perimeter wedges the distal tip 116 and the active fixation device1400 against the tissue of a vessel and lodges the lead assembly 100within the vessel. The active fixation device 1400 includes the texturedsurface 1408, optionally, to increase the secure coupling of the device1400 and lead assembly 100 to the vessel. In yet another option, theguide projection 1404 extends around the elongate body 102 and retainsthe active fixation device 1400 in secure engagement to the distal tip116 after the guide wire 202 is removed from the lumen 1402.

FIGS. 15 and 16 show an active fixation device 1500 coupled around theelongate body 102. The active fixation device 1500 includes, in oneoption, a nonlinear arched lumen 1502. An inner surface 1504 of theactive fixation device 1500 defines the non-linear arched lumen 1502 andengages against a portion of the elongate body 102. An electrode opening1506 extends between the outer perimeter 1508 and the inner surface1504. The portion of the elongate body 102 disposed within the archedlumen is bowed and extends through the electrode opening, in one option.In another option, the inner surface 1504 engages against the elongatebody 102 and pushes the portion of the elongate body 102 through theelectrode opening 1506. In one option, the elongate body 102 includes anelectrode 1510 coupled around the elongate body 102 and the electrode1510 extends, at least partially, through the electrode opening 1506.Optionally, the inner surface 1504 pushes the elongate body 102including the electrode 1510 into contact with a surface 1512surrounding the active fixation device 1500, such as a vein or an arterywall. In another option, the active fixation device 1500 has asufficiently large outer perimeter 1508 so the surface 1512 engages andstretches around the device 1500. In one option, as shown in FIG. 15,the outer perimeter of the active fixation device 1500 graduallyincreases toward the proximal end of the device 1500 to enhanceengagement of the lead assembly 100 to the surface 1512. The surroundingsurface 1512, in another option, grasps the outer perimeter 1508 andimmobilizes the device 1500 and the lead assembly 100. Optionally, aplurality of fixation devices 1500 are coupled around the elongate body102. The fixation devices 1500, in one option, have differing sizesand/or textured surfaces (described below).

In another option, the active fixation device 1500 includes a texturedsurface, for instance at least one tine 1514. The tine 1514 engagesagainst the surface 1512 to securely couple the active fixation device1500 where desired along the elongate body, for example around theelectrode 1510. Optionally, the tine 1514 extends from the outerperimeter 1508 toward the proximal end 106 (FIG. 1) of the elongate body102. The tine 1514 substantially prevents movement of the activefixation device 1500 toward the proximal end 106 once the activefixation device is positioned within a vessel, such as a vein or anartery. In yet another option, the textured surface includes, but is notlimited to ridges, knurling, mesh material, slots, holes or the like. Inone option, shown in FIG. 16, slots 1515 extend along the activefixation device 1500 and are provided to enhance blood flow around theactive fixation device 1500.

Optionally, the active fixation device 1500 includes a drug (e.g., ananti-inflammatory agent) that is emitted over time. Various drugs areplaced in active fixation devices moveably coupled to the elongate body,in another option, for localized therapy where desired around a heart.

In operation, after positioning of the lead assembly 100 within thevasculature the active fixation device 1500 is guided over the elongatebody 102 and pushed toward a desired position along the elongate body102 with the push tube 122. In one option, the active fixation device1500 is moved over the electrode 1510. The elongate body 102 includingthe electrode 1510 is disposed in the arched lumen 1502. The innersurface 1504 pushes the elongate body 102 and the electrode 1510 throughthe electrode opening 1506. In another option, when pushed through theelectrode opening 1506, the electrode 1510 is engaged against a surface1512, for instance the walls of a vein or artery. The active fixationdevice 1500 optionally has an oval cross section to preferentiallyorient the electrode 1510 within a coronary vessel and engage theelectrode 1510 against the surface 1512 toward the myocardium of aheart. The curve of the elongate body 102 induced by the inner surface1504 ensures consistent electrical communication between the surface1512 and the electrode 1510. Additionally, deformation of the elongatebody 102 by the active fixation device 1500 creates a friction fitbetween the elongate body 102 and the active fixation device 1500, inone option. The active fixation device 1500, in another option,increases the outer perimeter of the lead assembly 100 and therebysecurely couples the lead assembly 100 to the surface 1512 at thedesired position along the elongate body 102. In yet another option, thetine 1514 engages with the surface 1512 and substantially preventsmovement of the active fixation device 1500 toward the proximal end 106(FIG. 1) of the elongate body 102.

FIGS. 17A and 17B illustrate another example of an active fixationdevice 1700 slidably coupled around the elongate body 102. In oneoption, the push tube 122 is coupled around the elongate body 102 andthe push tube distal end 206 is engaged against an end 1702 of theactive fixation device 1700 (FIG. 17A). In another option, the activefixation device 1700 has an outer perimeter 1704 larger than thecorresponding outer perimeter 1706 of the elongate body 102. The outerperimeter 1704, optionally, is sized and shaped to stretch surfaces ofsurrounding vasculature and lodge the active fixation device 1700 withinthe vasculature. In one option, the surrounding walls grasp andimmobilize the active fixation device 1700. In another option, theactive fixation device 1700 includes a deformable material (e.g.silicone rubber or the like) that deforms when surrounded and grasped bythe vasculature. Deformation of the active fixation device 1700 pinchesaround the elongate body 102 and immobilizes the lead assembly 100relative to the active fixation device lodged in the vasculature.

In another option, the outer perimeter 1704 of the active fixationdevice 1700 includes a textured surface having, for instance, ridges,knurling, mesh material or the like. In one option, the textured surfaceincludes tines 1708. The active fixation device 1700 shown in FIGS. 17Aand 17B includes two tines 1708. In another example, the active fixationdevice 1700 includes one or more tines 1708. The tines 1708, in anotheroption, lay back adjacent to the outer perimeter 1704 and point towardthe proximal end 106 (FIG. 1) of the elongate body 102. The tines 1708are sized and shaped, optionally, to engage against the surfaces of thevasculature and immobilize the active fixation device 1700.

In yet another option, the outer perimeter 1704 textured surfaceincluding at least the tines 1708 is constructed with an expandablematerial, such as a hydrogel or the like. As shown in FIG. 17B, thetines 1708 swell as the hydrogel absorbs water from the surroundingvasculature. In one example, the expandable material includes asemi-permeable membrane that forms an outer surface of the tines 1708.The semi-permeable membrane provides an osmolarity imbalance between thetines and the fluids of the surrounding vasculature. Water permeates themembrane and swells the tines 1708 into the position shown in FIG. 17B,Prior to expansion, in one option, the tines 1708 remain substantiallyadjacent to the outer perimeter 1704 of the active fixation device 1700(See FIG. 17A). In this orientation, the tines 1708 slightly alter theprofile of the active fixation device 1700 and have substantially littleinfluence on tracking of the active fixation 1700 along the elongatebody 102 through the vasculature. In the expanded position (FIG. 17B)the tines 1708 curl away from the outer perimeter 1704 and substantiallyincrease the profile of the active fixation device 1700. Expansion ofthe tines 1708 occurs after positioning the active fixation device 1700optionally, where it is desirable to immobilize the lead assembly 100within the vasculature.

In operation, the active fixation device 1700 is coupled around theelongate body 102 and moved with the push tube 122 engaged to the end1702 of the device 1700 and also coupled around the elongate body 102.The push tube 122 pushes the active fixation device 1700 to a desiredlocation in the vasculature, and the push tube 122 is then withdrawn.Optionally, the push tube 122 remains engaged to the active fixationdevice 1700 to hold the device 1700 in place along the elongate body102. In one option, the textured surface, including the tines 1708around the outer perimeter 1704 engage against the vasculature toimmobilize the active fixation device 1700. In another option, as shownin FIG. 17B, the tines 1708, including a material such as a hydrogel ora semi-permeable membrane, expand and securely engage against thesurfaces of the vasculature to immobilize the active fixation device1700. Optionally, the active fixation device 1700 is interchangeablewith other active fixation devices having different sizes and texturedsurfaces. In one option, a particular active fixation device is chosenbased on size and the desired textured surface and coupled around theelongate body 102 and moved into a desired position with the push tube122. Optionally, the push tube 122 is a catheter tube advanced throughan outer catheter to position the active fixation device 1700 along theelongate body 102.

FIGS. 18A and 18B illustrate another active fixation device 1800 similarin some respects to the active fixation device 1700 (FIGS. 17A and 17B).The active fixation device 1800 is slidably coupled around the elongatebody 102. In one option, the active fixation device 1800 includes atextured surface including, for instance, tines 1708. In anotherexample, the textured surface includes, but is not limited to, ridges,knurling, mesh material or the like. In another option, the tines 1708include an expandable material such as a hydrogel or a semi-permeablemembrane. The tines 1708, optionally, expand and curl away from theouter perimeter 1804 of the active fixation device 1800 (See FIG. 18B)to securely engage with vasculature surrounding the lead assembly 100.

The active fixation device 1800 shown in FIGS. 18A and 18B is coupledaround the guide wire 202. In one option, the push tube 122 is engagedagainst the end 1802 of the active fixation device 1800 and coupledaround the guide wire 202 (FIG. 18A). In another option, the push tube122 is moved over the guide wire 202 and the push tube 122correspondingly moves the active fixation device 1800 along the elongatebody 102. Coupling the active fixation device 1800 around the guide wire202 and the elongate body 102, in one option, ensures the device 1800 isretained in a desired orientation on the elongate body 102. In anotheroption, the active fixation device 1800 is substantially prevented fromrotating around the elongate body 102 during movement along the body 102because it is coupled around the guide wire 202 adjacent to the body102.

FIG. 19A-F are side views of an active fixation device 1900 moveablycoupled around the elongate body 102. In one option, the elongate body102 includes a flange 1902 distal to the active fixation device 1900.The active fixation device 1900 is sized and shaped to engage againstthe flange 1902. The push tube 122 is engaged against the proximal end1904 of the active fixation device 1900. The push tube 122 operates tolongitudinally compress the active fixation device 1900 between theflange 1902 and the push tube 122, as described below. In anotheroption, the active fixation device 1900 is integral with the elongatebody 102 distal to the active fixation device 1900. The active fixationdevice 1900, in yet another option, is integral to the push tube 122.The active fixation device 1900, optionally, is constructed with, butnot limited to a polymer, such as polyurethane. In another option, theactive fixation device 1900 is constructed with materials substantiallysimilar to the elongate body 102.

As shown in FIG. 19A, the active fixation device 1900 includes at leastone opening. In the example shown in FIGS. 19A-D, the active fixationdevice includes a plurality of openings 1906A-C sized and shaped tofacilitate compression and radial expansion of the active fixationdevice 1900 when the push tube 122 is axially moved along the elongatebody 102 toward the flange 1902. Members 1912A-C are disposed adjacentto the openings 1906A-C. As described below, the members 1912A-C aresized and shaped to radially expand as the active fixation device 1900is compressed (See FIGS. 19B, C). The openings 1906A-C are formed in theactive fixation device by a variety of methods, including etching, lasermachining or the like. The openings 1906A-C include, in one option,recesses 1908 sized and shaped to facilitate radial expansion of theopenings 1906A-C with pushing forces delivered by the push tube 122 tothe active fixation device 1900. The recesses 1908, in another option,substantially prevent pinching of the members 1912A-C to close theopenings 1906A-C.

In yet another option, the openings 1906A are spaced radially around theactive fixation device 1900. Openings 1906B, C are also spaced radiallyaround the active fixation device 1900, optionally. The openings 1906Aare radially spaced from each other by an offset 1910A. Similarly in oneoption, the openings 1906B, C are radially spaced from each other byoffsets 1910B, C, respectively. In one option, the offsets 1910A-Ccorrespond to the width of the members 1912A-C. The offsets 1910A-C,gradually increase optionally from the proximal end 1904 toward theflange 1902. Increasing the offsets 1910A-C gradually increases thecolumn strength of the members 1912A-C toward the flange 1902. Theincreased column strength at each set of openings 1906A-C requiresprogressively greater pushing forces to radially expand the members1912A-C. As shown in FIG. 19B, increasing the offsets 1910A-C in thismanner allows pushing forces transmitted by the push tube 122 toselectively expand the members 1912A adjacent the proximal end 1904first. The members 1912B, C subsequently expand radially with themembers 1912B expanding first because the offset 1910B is smaller forthe members 1912B.

In one option, the openings 1906A-C increase in length between theproximal end 1904 and the flange 1902. The members 1912A-C therebygradually increase in length between the proximal end and the flange1902. The members 1912B, C correspondingly project further from theactive fixation device 1900 than the members 1912A (FIG. 19C). The pushtube 122 is advanced along the elongate body 102 to compress the activefixation device 1900 and selectively extend members 1912A-C. In oneoption, the active fixation device 1900 is disposed in a smaller vesseland the smaller members 1912A are only necessary to retain the elongatebody 102 within the vessel, In another option, the active fixationdevice 1900 is disposed in a larger vessel (e.g. the vessels around aheart) and the longer members 1912B, C extend from the device 1900 withincreased pushing forces applied through the push tube 122. Optionally,the members 1912A-C adjustably extend from the active fixation device1900 in accordance with the pushing force applied through the push tube122. In one option, greater pushing force applied through the push tube122 causes the active fixation device 1900 to compress further and themembers 1912A-C to correspondingly extend farther. The members 1912A-Cadjustably extend from the active fixation device 1900 to engage againsta variety of surfaces, for example vasculature with differing innerdiameters.

In another option, the increasing offsets between the proximal end 1904and the flange 1902 facilitate selective radial expansion of members1912A-C by requiring greater and greater pushing forces to overcome theincreasing column strengths provided by the progressively larger offsets1910A-C. In one option, a physician applies a set amount of pushingforce through the push tube 122 to the active fixation device 1900 toextend only the members 1912A. In another option, shown in FIG. 19C,additional pushing force is applied to extend the members 1912B and/orC.

Optionally, the offsets 1910A-C and the lengths of openings 1906A-C arevaried to obtain a variety of projection profiles that extend from thelead assembly 100. For instance, offset 1910C is the smallest and themembers 1912C are thereby the first to project with movement of the pushtube 122 toward the active fixation device 1900. In another example,openings 1906B are the longest and thus form the largest members 1912B.

In another option, increased pushing forces applied through the pushtube 122 further longitudinally compress the active fixation device1900, as shown in FIG. 19D. The compression of active fixation device1900 continues to extend the members 1912A-C (FIGS. 19A-C) until themembers 1912A-C fold back on themselves and form tines 1914A-C.Optionally, as with the members 1912A-C, the tines 1914B, C extend fromthe active fixation device 1900 further than the tines 1914A. Theincreased size of the tines 1914A-C relative to the radially extendedmembers 1912A-C, in one option, provides enhanced engagement of theactive fixation device 1900 to surfaces, such as a vessel or themyocardium of a heart.

Optionally, the active fixation device 1900 includes regions havingdecreased wall thickness and/or creases around a radius of the device1900. The push tube 122 operates to compress these regions and form atleast one radial projection extending around the active fixation device.In another option, the openings 1906A-C extend helically around theactive fixation device 1900. Pushing or twisting of the push tube 122operates to correspondingly compress or twist the active fixation device1900 and extend the members 1912A-C. In still another option, the activefixation device 1900 includes only openings 1906A to form radiallyprojecting members 1912A and/or tines 1914A. The active fixation device1900, in yet another option, includes a single opening 1906A and asingle member 1912A is adjacent to the opening 1906A.

Optionally, the active fixation device 1900 includes cavities that forma mesh pattern in the device 1900 so the device 1900 has a weakenedcolumn strength between the proximal end 1904 and the flange 1902. Whencompressed or twisted, the mesh pattern bows away from the elongate body102 to form at least one projection. The active fixation device 1900includes elongate elements (e.g. wires, ribbons or the like), in oneoption. The elements bow away from the elongate body 102, whencompressed or twisted by the push tube 122, to form at least oneradially projecting member. The elements, optionally, include, but arenot limited to, super-elastic metals, such as Nitinol. In anotheroption, the elements are formed with a microcoil including a film (e.g.0.001 inches thick) that is wrapped into a coil. Optionally, theelements are woven or braided into a mesh and the mesh bows away fromthe elongate body 102, when compressed or twisted.

In another option, the active fixation device 1900 is radiopaque tofacilitate visualization of the device 1900 during implantationprocedures. Optionally, the active fixation device 1900 includes aconductive material (e.g. Nitinol) and acts as an electrode when coupledwith the conductor 110 (FIG. 1). One or more of the active fixationdevice 1900, the elongate body 102 and the push tube 122 includefluoropolymers, in yet another option, to facilitate sliding movementbetween the push tube 122 and the elongate body 102 and/or the device1900 and the elongate body 102. Optionally, a lubricious coating isapplied between one or more of the active fixation device 1900, theelongate body 102 and the push tube 122 to facilitate sliding movementtherebetween. In a further option, one or more of the active fixationdevice 1900 and the push tube 122 are coextruded with a lubricouspolymer forming the inner diameter.

In operation, the lead assembly 100 including the active fixation device1900 having openings 1906A is positioned within the vasculature, forinstance, the tortuous vasculature around the left side of the heart. Asshown in FIG. 19E, in one option, the active fixation device 1900 is ina first unexpanded position during navigation of the lead assembly 100through the vasculature. When the lead assembly 100, includingoptionally the electrode 112, is positioned where desired, the push tube122 is advanced toward the active fixation device 1900. Referring now toFIG. 19F, the push tube 122 transmits pushing forces to the proximal end1904 thereby compressing the active fixation device 1900. Compression ofthe active fixation device 1900 radially expands the members 1912A fromthe device 1900. The active fixation device 1900 assumes a secondradially expanded position. The members 1912A engage against asurrounding surface (e.g. a vessel wall and/or the myocardium of aheart). In another option, the push tube 122 is further advanced towardthe active fixation device 1900 and the members 1912A fold back onthemselves to form tines 1914A (FIG. 19D).

Referring again to FIG. 19F, a gap 1916 is formed between the push tube122 and the lead terminal 1918. To retain the active fixation device1900 at the desired location on the elongate body 102 and/or in thecompressed state a stop 1920, such as a suture sleeve, is disposedwithin the gap 1916. The stop 1920, in one option, is sized and shapedto snugly fit within the gap 1916 and overlay a portion of the push tube122 and the lead terminal 1918 (e.g. a flexible boot proximal toelectrical terminal contacts). Optionally, a spacer clip is placedwithin the gap 1916 to immobilize the active fixation device 1900, andthe stop 1920 covers the spacer clip. In another option, the stop 1920is deformable and slid over the lead terminal 1918 to position the stop1920 within the gap 1916. In yet another option, the stop 1920 is formedaround the push tube 122 distal to the lead terminal 1918 and slid intothe gap 1916 after expansion of the active fixation device 1900.Optionally, the stop 1920 is slit along one side and pressed over theelongate body 102 and the push tube 122 to retain the active fixationdevice 1900 at the desired location and/or in the compressed state withthe members 1912A extended. In another option, suturing is performedaround the stop 1920 to snugly engage the stop 1920 to the elongate body102 and immobilize the active fixation device 1900.

Optionally, removal of the stop 1920 from within the gap 1916 permitsremoval of the lead assembly 100 from within the vasculature. In oneoption, the stop 1920 is deformed to pull the stop 1920 out of the gap1916. The push tube 122 is pulled toward the lead terminal 1918,optionally, and away from the active fixation device 1900. The activefixation device 1900 includes, in another option, a deformable material(e.g. polyurethane) and longitudinally expands to assume the profileshown in FIG. 19E as the push tube 122 is retracted. In one option, theactive fixation device 1900 radially contracts as the device 1900longitudinally expands. Optionally, the push tube 122 is coupled to theproximal end 1904 of the active fixation device 1900 and pulling of thepush tube 122 correspondingly pulls and longitudinally expands thedevice 1900 as shown in FIG. 19E. The lead assembly 100 with theradially contracted active fixation device 1900 is retracted out of thevasculature.

FIG. 20 is a cross sectional view of an active fixation device 2000substantially surrounded by the push tube 122. In one option, the activefixation device 2000 is a deformable cable. In another option, theactive fixation device 2000 has a predetermined non-linear shape, forinstance, a spiral, zigzag or the like. The deformable cable, in oneoption, includes a shape memory material such as Nitinol. In anotheroption, in larger vessels and/or with less tortuous vasculature, thedeformable cable is formed with filars coiled in a pattern to providethe predetermined non-linear shape. The active fixation device 2000 ispreformed with the predetermined shaped (e.g., a molded polymer or thelike), in yet another option.

The push tube 122 is formed of a sufficiently rigid material (e.g.stainless steel, polymer or polymer including a metal braid) tostraighten the active fixation device 2000 when the push tube 122 iscoupled around the device 2000. In one option, the push tube 122 isslidably coupled to the active fixation device 2000 and moved over thedevice 2000 toward a distal end 2002 of the device 2000. The push tube122 straightens the non-linear shape of the active fixation device 2000as it is moved over the device 2000. In another option, where the activefixation device 2000 includes Nitinol, the predetermined shape isstraightened prior to coupling with the push tube 122 and heat (e.g.,body heat) is used to provide the predetermined non-linear shape.Optionally, the push tube 122 provides column strength to the activefixation device 2000 to move the device 2000 toward the distal end ofthe elongate body 2100 (See FIG. 21).

In one option, a seat 2004 sized and shaped to receive the push tubedistal end 206 is coupled to the active fixation device 2000. The seat2004, in another option, extends radially from the distal end 2002 ofthe active fixation device 2000. In yet another option, the seat iscrimped, welded or the like around the active fixation device 2000. Theseat 2004 and the push tube distal end 206 include, optionally, a keyand corresponding notch to prevent relative rotation between the pushtube 122 and the active fixation device 2000. In another option, thepush tube distal end 206 and the seat 2004 are non-circular and engageagainst each other to prevent relative rotation therebetween. The pushtube 122, in yet another option, is rotated to turn the active fixationdevice 2000 and couple the device 2000 with the elongate body 2100,described below.

FIG. 21 is a cross sectional view of the elongate body 2100 slidablycoupled around the active fixation device 2000 and the push tube 122.Optionally, the elongate body 2100 includes a distal tip 2101. Thedistal tip 2101 is deformable (e.g. silicone rubber), in another option,to facilitate navigation in tortuous vasculature, such as around theleft side of a heart. Where the active fixation device 2000 is adeformable cable, the deformable cable has a sufficiently small profileto permit navigation of the correspondingly sized elongate body 2100through tortuous vasculature. In one option, the elongate body 2100includes a fastener 2102 substantially adjacent to a distal end 2104. Inanother option, the fastener 2102 includes threading that extends aroundthe distal end 2004 of the active fixation device 2000. In yet anotheroption, the fastener 2102 includes a snap fitting, adhesive or the like.The fastener 2102 is sized and shaped to securely couple the distal end2002 of the active fixation device 2000 to the distal end 2104 of theelongate body 2100. In another option, the distal end 2004 of the activefixation 2000 device includes a corresponding fastener 2106 sized andshaped to engage with the fastener 2102 and securely couple the device2000 to the elongate body 2100. Optionally, the active fixation device2000 is immobilized with respect to the elongate body 2100 when coupledto the elongate body 2100. The active fixation device fastener 2106, inan option, includes threading corresponding to the threading of thefastener 2102. The push tube 122 engages against the seat 2004 and movesthe active fixation device through the elongate body 2100 toward thedistal end 2104, in one option. In another option, the push tube 122 isrotated to couple the fastener 2102 with the active fixation device 2000(e.g. the active fixation device fastener 2106) substantially adjacentto the distal end. Optionally, the threading of the fastener 2106engages with corresponding threading on the fastener 2102.

FIG. 22 is a cross sectional view of the active fixation device 2000engaged against an inner surface 2200 of the elongate body 2100. In oneoption, the push tube 122 is withdrawn from around the active fixationdevice 2000 to allow the device 2000 to assume the predeterminednon-linear shape. In another option, the push tube 122 is withdrawn andthe active fixation device 2000 including Nitinol is exposed to heat(e.g., body heat). The heat induces the active fixation device 2000 toassume the non-linear predetermined shape and engage against theelongate body 2100. Engagement of the active fixation device 2000 withthe inner surface 2200 moves the elongate body 2100 into a non-linearshape corresponding to the predetermined nonlinear shape of the activefixation device. In one example, the elongate body 2100 assumes acorresponding non-linear shape when the non-linear active fixationdevice 2000 engages against the inner surface 2200. The elongate body2100 correspondingly engages against a surface 2206 such as the wall ofa vein or artery and/or the myocardium of a heart, in one option, andimmobilizes the elongate body 2100 within the vasculature.

In another option, at least a portion of the inner perimeter 2202 of thepush tube 122 is non-circular. The active fixation device optionallyincludes a lug 2204 having a corresponding size and shape to thenon-circular inner perimeter 2202 of the push tube 122. As the push tube122 is withdrawn from around the active fixation device 2000, as shownin FIG. 22, the inner perimeter 2202 of the push tube 122 is coupledaround the lug 2204. One example of the coupling between the push tube122 and the lug 2204 is shown in the sectional view of FIG. 23. Theinner surface 2202 has a hexagonal geometry, in the example shown. Inanother example, the inner surface 2202 has a triangular, square, ovulargeometry or the like. The outer perimeter of the lug 2204 has acorresponding non-circular geometry. In another option, the activefixation device is coupled around the push tube and the active fixationdevice has a non-circular inner perimeter and the push tube has acorresponding non-circular outer perimeter.

Optionally, the push tube 122 is rotated and the non-circular innerperimeter 2202 engages against the corresponding non-circular lug 2204to rotate the active fixation device 2000 as desired. Referring again toFIG. 22, in one option, the active fixation device 2000 is rotatedwithin the elongate body 2100 to twist the device 2000 andcorrespondingly twist the elongate body 2100 coupled thereto. In oneexample, the active fixation device 2000 is rotated to improve contactbetween the elongate body (e.g. electrodes coupled to the elongate body)and the surface 2206, for instance, the electrically active myocardiumof the heart. In another example, the active fixation device 2000 isrotated to change the engagement of the elongate body 2100 with thesurface 2206, for instance, to enhance the immobilization of theelongate body 2100 within the vasculature.

FIG. 24 is a block diagram illustrating a method 2400 for positioning alead assembly (e.g., a side rail lead assembly). At 2402, the leadassembly is guided over a guide wire. The guide wire is slidably coupledto a side rail seat. The side rail seat is substantially adjacent to thedistal end of the lead assembly and disposed along the lead (e.g.juxtaposed to the lead). At 2404, a push tube is moved over the guidewire and the side rail seat and the lead correspondingly move with thepush tube. In one option, the push tube is slidably coupled around theguide wire. The push tube is coupled to the side rail seat in anotheroption. In another option, the method 2400 includes coupling the pushtube with the side rail seat. Coupling the push tube with the side railseat includes, optionally, seating at least a push tube distal endwithin a socket in the side rail seat. In one option, a surface definingthe socket is sized and shaped to immobilize at least the push tubedistal end. In yet another option, the side rail seat and the leadassembly are rotated with the push tube. The push tube is twisted torotate the side rail seat and the lead assembly, in one option.Optionally, coupling the push tube with the side rail seat includescoupling a push tube distal end having a key with the side rail seathaving a corresponding recess. The method 2400, in another option,includes deflecting at least a push tube distal end, wherein the pushtube distal end is more flexible than another portion of the of pushtube. Optionally, the guide wire is exchanged for a second guide wire.In one option, relative to the guide wire, the second guide wire has adifferent flexibility or predetermined shape.

In one option, the method 2400 includes moving an active fixation deviceover the guide wire toward the lead assembly distal end with the pushtube, wherein the push tube is coupled to the active fixation device. Inanother option, the push tube is uncoupled from the side rail seat tocouple with the active fixation device. The active fixation device iscoupled with a distal tip, optionally, and the distal tip is coupled tothe elongate body substantially adjacent to the distal end. In oneoption, a combined outer perimeter of the active fixation device and thedistal tip is greater than an outer perimeter of the distal tip. Inanother option, the active fixation device is coupled with the distaltip by engaging a pawl with a rack and inhibiting movement of the activefixation device away from the distal tip. In yet another option, theactive fixation device is immobilized in surrounding tissue. The activefixation device, in one example, is immobilized by wedging the activefixation device and the distal tip within a vein or artery. In anotherexample, the active fixation device expands to immobilize the device inthe surrounding tissue. Optionally, immobilizing the active fixationdevice includes disposing a tine in the surrounding tissue.

The above described lead assembly allows for implantation of slenderleads through tortuous vasculature (e.g. coronary veins around the leftside of the heart) using a push tube. In one option, the lead assemblyincludes a distal tip sized and shaped to couple with a push tube thatextends along at least a portion of the elongate body. A pushing forceis applied to the push tube and transmitted to the distal tip to pushthe distal end of the elongate body through vasculature and into oraround the heart (e.g., into the epicardium of the heart). In oneoption, a portion of the elongate body proximal to the distal tip andcoupled thereto is pulled as the distal tip is pushed by the push tube.In another option, the distal tip includes a seat. The push tube and theseat include, optionally, non-circular perimeters or a key and a recess.The push tube is rotated to correspondingly rotate the distal tip into adesired orientation for optimum electrode to tissue contact, in oneoption. In another option, the push tube is rotated to turn the distaltip and the elongate body and allow for easier navigation of thevasculature.

Because the push tube is fed over the guide wire or over the elongatebody, a stylet lumen or the like is not necessary. In one option, theelongate body has a has a smaller cross-section and is less invasivethan leads having a stylet lumen. The lead assembly includes additionalconductors or the like in the space occupied by a stylet lumen, inanother option. The conductors of the lead assembly described hereininclude cables that extend substantially linearly along the elongatebody because a stylet lumen formed with coiled conductors is notnecessary. Linear cables take up less space within the elongate body, ascompared to coiled conductors, and allow for a lead assembly with asmaller outer perimeter that also has multiple conductors andcorresponding electrodes. In yet another option, a lumen is formedwithin the elongate body and is sized and shaped to receive the pushtube and the guide wire and the push tube is fed over the guide wire tonavigate the elongate body through vasculature. Having a push tube lumenwithin the elongate body decreases the profile of the elongate bodyallowing for easier navigation of the lead assembly. Additionally, thepush tube provides increased column strength compared to, for example, astylet. The increased column strength enhances the transmission ofpushing forces through the push tube to the elongate body.

Moreover, the push tube (e.g. tubing, integral tubing, catheter, or thelike) of the lead assembly allows for the positioning of a variety ofactive fixation devices into desired orientations along the elongatebody, for instance, after the elongate body is positioned withinvasculature and/or a heart. The elongate body tracks through thevasculature easily without the active fixation devices disposed alongthe elongate body until after implantation of the elongate body. In oneoption, the active fixation devices have a larger profile than theelongate body and are introduced after the elongate body is positionedas desired within a heart and/or the vasculature. In another option,when the active fixation device and distal tip are coupled the combinedouter perimeter engages the surrounding vasculature of, for example, avein or artery, and securely couples the elongate body with thevasculature. In another option, active fixation devices sized and shapedto deform the elongate body are advanced along the elongate body. In oneoption, the active fixation devices deform and push the elongate body(e.g. including electrodes) into snug engagement with the vasculature.In another option, active fixation devices are actuated with the pushtube (e.g. by rotating the push tube to turn a threaded fixation device)to couple with surfaces within the vasculature or on the epicardialsurfaces of a heart.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. It should be noted that embodiments discussed indifferent portions of the description or referred to in differentdrawings can be combined to form additional embodiments of the presentapplication. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1. An apparatus comprising: an elongate body extending from a proximalend to a distal end; a conductor disposed within the elongate body; anelectrode coupled to the elongate body, wherein the electrode is inelectrical communication with the conductor; a push tube extending alongat least a portion of the elongate body; and a distal tip coupled to theelongate body substantially adjacent to the distal end, wherein thedistal tip is sized and shaped to couple with a push tube distal end. 2.The apparatus of claim 1, wherein at least a portion of an outerperimeter of the distal tip includes a seat sized and shaped to receivea push tube distal end.
 3. The apparatus of claim 2, wherein at leastone of the push tube distal end and the seat has a noncircular outerperimeter and the other of the push tube distal end and the seat has acorresponding inner perimeter.
 4. The apparatus of claim 2, wherein theelongate body is substantially adjacent to the push tube and the seat.5. The apparatus of claim 2, wherein the seat includes a socket sizedand shaped to grasp and immobilize the push tube distal end.
 6. Theapparatus of claim 5, wherein the seat includes a deformable coildisposed within the socket, and the deformable coil has an innerperimeter smaller than the outer perimeter of the push tube.
 7. Theapparatus of claim 1, wherein the outer perimeter of the distal tiptapers from a proximal portion of the distal tip toward a distal portionof the distal tip.
 8. The apparatus of claim 1, wherein the distal tipincludes an active fixation device.
 9. The apparatus of claim 8, whereinthe active fixation device includes at least one slot extendingsubstantially along the active fixation device.
 10. The apparatus ofclaim 1, wherein the distal tip includes an exit groove sized and shapedto immobilize at least a portion of the elongate body.
 11. The apparatusof claim 1, wherein at least a first portion of the push tube is moreflexible than a second portion of the push tube.
 12. The apparatus ofclaim 11, wherein the push tube distal end is more flexible than thesecond portion of the push tube.
 13. The apparatus of claim 11, whereinat least the portion of the push tube includes a groove extending atleast part way between an outer perimeter of the push tube and an innerperimeter of the push tube.
 14. An apparatus comprising: an elongatebody extending from a proximal end to a distal end; a conductor disposedwithin the elongate body; an electrode coupled to the elongate body,wherein the electrode is in electrical communication with the conductor;a push tube extending along at least a portion of the elongate body; anda side rail seat coupled along the elongate body substantially adjacentto the distal end, wherein the side rail seat includes: a socketdisposed along the elongate body, and the socket is sized and shaped toreceive a push tube distal end, and a guide wire lumen defined by aninner surface of the side rail seat, wherein the guide wire lumen issubstantially concentric with the socket.
 15. The apparatus of claim 14,further comprising: a guide wire extending along at least the portion ofthe elongate body and disposed within the guide wire lumen, wherein theguide wire is slidably coupled to the side rail seat.
 16. The apparatusof claim 15, wherein the push tube is slidably coupled around the guidewire.
 17. The apparatus of claim 14, wherein at least a portion of theguide wire lumen is oblique with respect to the distal end of theelongate body.
 18. The apparatus of claim 14, further comprising adistal tip coupled to the elongate body substantially adjacent to thedistal end, wherein the distal tip includes the side rail seat.
 19. Theapparatus of claim 18, wherein a first outer perimeter of a proximalportion of the distal tip is larger than a second outer perimeter of adistal portion of the distal tip.
 20. The apparatus of claim 14, whereinthe socket has a noncircular inner perimeter and the push tube has acorresponding outer perimeter to the socket.
 21. The apparatus of claim14, wherein at least one of the push tube and the side rail seatincludes a key substantially adjacent to the push tube distal end, andthe other of the side rail seat and the push tube includes acorresponding recess to receive the key.
 22. The apparatus of claim 14,further comprising an active fixation device slidably coupled with theelongate body, wherein the active fixation device is sized and shaped toengage with the push tube.
 23. A method comprising: guiding a leadassembly over a guide wire, wherein the guide wire is slidably coupledto a side rail seat substantially adjacent to a distal end of the leadassembly, and the side rail seat is disposed along the lead assembly;and moving a push tube over the guide wire, wherein the push tube iscoupled to the side rail seat, and the side rail seat and lead assemblymove with the push tube.
 24. The method of claim 23, further comprisingcoupling the push tube with the side rail seat.
 25. The method of claim24, wherein coupling the push tube with the side rail seat includesseating at least a push tube distal end within a socket in the side railseat, wherein a surface defining the socket is sized and shaped toimmobilize at least the push tube distal end.
 26. The method of claim24, wherein coupling the push tube with the side rail seat includescoupling a push tube distal end having a key with the side rail seathaving a corresponding recess.
 27. The method of claim 23, furthercomprising rotating the side rail seat and lead assembly with the pushtube.
 28. The method of claim 23, further comprising deflecting at leasta push tube distal end, wherein the push tube distal end is moreflexible than another portion of the push tube.
 29. The method of claim23, further comprising moving an active fixation device over the guidewire toward the lead assembly distal end with the push tube, wherein thepush tube is coupled to the active fixation device.
 30. The method ofclaim 29, further comprising uncoupling the push tube from the side railseat.
 31. The method of claim 29, further comprising coupling the activefixation device with a distal tip and the distal tip is coupled to theelongate body substantially adjacent to the distal end, wherein acombined outer perimeter of the active fixation device and the distaltip is greater than an outer perimeter of the distal tip.
 32. The methodof claim 31, wherein coupling the active fixation device with the distaltip includes engaging a pawl with a rack and inhibiting movement of theactive fixation device away from the distal tip.
 33. The method of claim31, further comprising immobilizing the active fixation device insurrounding tissue including wedging the active fixation device and thedistal tip within a vein or artery.
 34. The method of claim 29, furthercomprising immobilizing the active fixation device in surroundingtissue.
 35. The method of claim 34, wherein immobilizing the activefixation device in surrounding tissue includes expanding the activefixation device.
 36. The method of claim 34, wherein immobilizing theactive fixation device in surrounding tissue includes engaging atextured surface against surrounding tissue.
 37. The method of claim 23,further comprising exchanging the guide wire for a second guide wire.